The Role of HnRNPA1 in T Cell-Mediated Gut Tolerance

Abstract Our previous research showed that Akt phosphorylation of the RNA-binding protein, (RBP) heterogeneous nuclear ribonucleoprotein (hnRNP) A1, is dependent on TCR signal strength, and occurs under conditions of induced T regulatory (Treg) cell differentiation. We have shown hnRNPA1 is required for optimal Treg differentiation by performing knockdown experiments, and our present research is focused on identifying a role for Akt phosphorylation in hnRNPA1 function. HnRNPA1 is phosphorylated by Akt at S199 and our lab has generated a new mutant mouse model, hnRNPA1-S199A (mA1), in which hnRNPA1 will no longer be Akt-phosphhorylated. Our initial characterization of mA1 mouse model failed to reveal major abnormalities in immune cells populations at steady state except for changes in the Treg proportion in the mesenteric lymph nodes. To investigate the effect of the mA1 on the development of oral tolerance we used an adoptive transfer model in which OT-II mA1 or OT-II WT naïve T cells were transferred into congenic strains and then the mice were given OVA food. Results indicate that mA1 OT-II T cells have a proliferation defect in vivo and we also observed a significant reduction in the induction of OVA-specific Treg in the mA1 T cells. Similar results were obtained when adoptively transferred OT-II mA1 T cells were challenged with limiting doses of specific peptide, given iv. RNASeq analysis of the transferred mA1 and WT T cells is being performed. These results suggest that Akt phosphorylation of hnRNPA1 is necessary for T cell response to low dose antigen and Treg induction in vivo. Our studies identify a new mechanism by which RBP influence T cell proliferation and Treg differentiation which has implications for tolerance to food antigens in the gut. Supported by NIH (F31-AI152320-02) NIH (R01-AI125513-03)